Pyrolytic sublimation

Decomplexation of some metal complexes calls for drastic conditions. This is true for (/7-arene)(/7-cyclopentadienyl)iron(II) hexafluorophosphates, [FeAr(Cp)][PF6] [54, 55]. Although their chemical decomplexation is known [55 a], the most widely used method is pyrolytic sublimation at high temperatures (>200 °C) [55 b]. To evaluate MW irradiation as the method of decomplexation of such iron complexes, Roberts et al. performed the reaction in the presence of graphite [54]. They discovered that the yield of the free ligand from the [Fe( -N-phenylcarbazole)( -Cp)][PF6] complex (43) depended on the kind (flakes or powder) and amount of graphite, and on the irradia-... 

Stabilized carbon nucleophiles (e.g. from 3-diketones, 3-keto esters, malonate esters, etc.) can be aryl-ated by substitution for chloride on the arene in (Fe(arene)Cp] cation complexes.72-78 81 A base is necessary and two heterogeneous systems are favored potassium carbonate in DMF or potassium fluoride prepared on Celite-545. As usual in the [FeCp]+ system, detachment of the substituted arene requires somewhat extreme conditions, usually pyrolytic sublimation at 200 C.46 An example is given in equation (27). 

Figure 6.25(a) shows a novel process for the continuous production of fuels from waste plastics. The proposed process consists primarily of three reactors. A mixture of waste plastics is fed into a pyrolytic reactor with heat-medium-particles stirred by a helical impeller (Figure 6.25(b)), where melted plastics are hydrothermally decomposed with steam and the random scission of C-C bonds. The produced mixture of a heavy oil containing wax and sublimate material is carried by steam stream to the next reactor, which is filled with an FeOOH catalyst (i.e. a catalytic hydrolysis reactor). The gaseous... 

Controversy surrounds the solid-liquid-vapor triple point which recent studies place either at approximately 4000 K and approximately 1 atm (28, carbyne form) or at 4130 30 K and 120 10 atm (23, pyrolytic graphite). We doubt the latter triple point because the temperature is displaced by 400 to 800 kelvlns from the sublimation curves (19-22 and ref. cited therein). The nature of the observed phenomenon (22-24) has been questioned (][8) as well as the measurement of temperature (28, 2 t 24). Also controversial Is Whittaker s proposal (28) that several carbyne forms are more stable than graphite above 2600 K. Evidence Includes X-ray data which were Interpreted (18) to Indicate slow forward transitions, graphite carbynes, but rapid reverse transitions. These transitions might explain discrepancies observed in various Cp curves but alternative explanations are possible. We retain graphite as the reference state at all temperatures this arbitrary choice avoids the need to switch phases at the proposed transition point, sublimation point or melting point, all of which are subject to change. 

Metal-containing poly-p-xylylenes were synthesized from PX with organometallic substituents or from PX-metal co-condensates. In the latter case the PX vapors were mixed in the outlet of the pyrolytic tube with metal vapors produced by sublimation of the corresponding metal. Depending on the metal... 

Low-Z ceramics for high heat-flux component materials for fusion reactors have been tested by out-of-pile electron beams and by in-pile TEXTOR limiter tests. While pyrolytic a-BN shows high thermal shock resistivity (and its use on the limiter ion side rules out arcing), the main erosion occurs by sublimation decomposition. There is evidence that superthermal electrons play a significant role in the limiter erosion [143 to 150]. 

The structure of pyrolytic graphite also accounts for the fact that this material can exhibit tensile strengths of 20,000 psi in the a-b direction, while in the c direction the tensile strength is about 1500 psi. As with other graphites, the pyroljrtic form displays higher strengths at elevated temperatures, does not melt under normal pressures and sublimes above 3500°C. 

Rim-benzoannulated corannulenes have been of interest since they represent an obvious extension of the fullerene surface and could potentially serve as precursors for larger bowl syntheses. Several of these derivatives including benzocorannulene 23 [26], dibenzo[a,d]corannulene 24 [26a], dibenzo[a,g]corannulene 25 [16, 27] and tribenzo[a,d,j]corannulene 26 [26] were recently synthesized by FVP and/or non-pyrolytic methods. X-ray crystal structure determination of 25 was very recently achieved [28] on a crystal grown by sublimation and revealed an assembling of... 

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